A multi-device backhaul link topology in microwave networks can require communications links having a near-zero bit error rate (“BER”), i.e., 10−12 BER. That is, certain microwave networks cannot tolerate any transmission errors. These networks, however, also require low latency and low jitter. Typical links have a latency of a couple of hundred microseconds due to propagation delay. Microwave networks also include aggressive coding so recipient devices can correct any errors that may occur in the link by using error correction during decoding.
Backhaul links provide connectivity between base-stations or a base-station to a network. The receiver sensitivity at each base-station should be designed to accommodate for transmission losses in order to achieve the near-zero bit error rate. For example, the signal-to-noise ratio (SNR) at the receiver should be greater than 33 dB in order to achieve a 10−12 BER for a 1024 QAM constellation. To achieve the near-zero BER, a margin of 5 dB is typically included such that the target signal-to-noise ratio for the receiver design is 38 dB. Accordingly, a BER of 10−12 can be achieved even when fading or other losses occur. This margin also accommodates for phase hits or any other statistical impairments that cause frames to be disrupted.
Automatic repeat request (“ARQ”) protocols are used in Long Term Evolution (“LTE”), wireless fidelity (“WI-FI”), and other communication applications. However, such protocols are not utilized in microwave networks because of the associated increased latency. ARQ protocols are usually generated at the receiver to acknowledge every frame that has been successfully received. Accordingly, when an acknowledgement is not sent or a recipient indicates a lack of acknowledgement, the transmitter knows to retransmit the corresponding frame. As a result, ARQ increases the latency and jitter in the communications link. To eliminate jitter, an internal buffer can be used at each node. When a frame is correctly received, it is transmitted to the next node. When such buffer is used and an error frame occurs, the network suffers from a constant latency and the network cannot continuously transmit on the link. That is, when a buffer is provided at each node, the overall latency is increased and the total latency is the summation of latencies at each one of the nodes.